The invention relates to a driving arrangement for selectively drivable wheels of a motor vehicle bearing axle. Many such driving arrangements are known, but each suffers from its own disadvantages.
German Laid-open Pending Patent Application No. 3 407 918 discloses a driving arrangement for a motor vehicle four-wheel drive system with an engageable and disengageable main clutch in the main transmission of a selectively connectable front-wheel drive. Bidirectional free wheel overrunning clutches are provided in the hubs of each of the front wheels. In this way, the usual differential transmission between the drives of the two front wheels can be dispensed with. Instead, only direction changing gearing to convey the rotary driving motion from the main transmission to the hubs of the front wheels is necessary.
The disadvantage inherent in this driving arrangement, however, is that due to the bidirectional free wheel overrunning clutches, the front wheels cannot be braked through the driving connection. For braking purposes, braking elements would have to be provided on the front wheels themselves.
German Laid-open Pending Patent Application No. 3 308 398 provides a differential gear on the inner ends of two input half shafts. This simultaneously allows a differing rolling speed of the wheels driven via the input shafts and ensures driving of the wheels if the differential gear has a higher angular speed than the input shafts extending into it. To this end, the differential has sets of thrust rings with axially oriented intermeshing wedge-shaped teeth. In the event of differing angular speed between the thrust rings, the wedge-shaped teeth establish a connection between the input shaft or shafts and the differential gear via a cone or disc clutch. As soon as a wheel and, consequently, an input shaft, rotates at a higher speed than the differential gear, the frictional connection at the cone or disc clutch is interrupted and the wheel in question can rotate freely.
The main disadvantage of this driving arrangement is that the differential gear occupies a relatively large amount of space. When installed on a bearing axle carrying, for example, the drivable front wheels of a motor vehicle, this results in an undesirable reduction in the ground clearance. Additionally, the necessary large case incurs correspondingly large manufacturing costs.
European Patent Application No. 0 047 942, teaches a housing for a differential gear fixed to a bridge of a track-adjustable front wheel bearing axle or to a bearing bracket receiving the bridge so that it can swing. In a first embodiment, the front wheels are driven via input shafts extending between the differential gear and the wheel center. In a second embodiment, the bearing axle is a portal axle with two bevel gearings enabling adaptation of the driving parts to the profile of a profile axle provided in the drive train to the front wheels.
The first embodiment of this driving arrangement is disadvantageous because the housing and the input shafts extending from it limit the ground clearance of the motor vehicle too greatly, while the second embodiment is too expensive due to the two bevel gears. Moreover, in both embodiments, the front wheels are connected to one another via a conventional differential gear which has the drawback that when travelling on a bend or cornering, it leads to tire wear or ground shearing and, when travelling over ground of varying condition, it cannot transmit any driving force to the still adhering front wheel.
Finally, German Laid-open Pending Patent Application No. 2 930 298 teaches a driving arrangement having an input shaft with an input gear swivellably connected thereto. The input gear, in turn, transmits its rotary motion directly via a spur gearing to a wheel hub holding the corresponding front wheel.
In this driving arrangement, the input shaft extends through a rigid axle body which is not variable in its track width, and consequently cannot be used with bearing axles adjustable to different track widths. On the contrary, the front wheels must be provided with folding or adjustable rims if different track widths are to be set, which eliminates advantages described in the reference arising from the accommodation of the swivelling housing inside the wheel rim.
Furthermore, this driving arrangement has the inherent disadvantage that it needs a differential gear to compensate for the differing speeds of rotation of the two front wheels when travelling on a bend, which leads to a reduction in the ground clearance. Moreover, the differential cannot be adapted to different track widths.
Accordingly, the object of the invention is to provide a driving arrangement for selectively drivable wheels of a motor vehicle bearing axle which achieves optimum traction conditions without limiting the ground clearance of the motor vehicle, and which can also be adjusted to different track widths, as needed.